In order to let a wire cut electric discharging machine (hereinafter as wire cut EDM) achieve a high processing speed, a huge current must be provided, and therefore a large amount of energy must be supplied to the gap between the wire electrode of the wire cut EDM and the workpiece within a very short period of time (&lt;3 uS) for processing a workpiece. However, supplying a large amount of energy to the gap between the wire electrode and the workpiece during a poor condition may cause the wire electrode to be broken. Therefore, the amount of energy must be controlled during the process of discharge.
A conventional discharge control circuit of a wire cut EDM, as shown in FIG. 1, is a transistor-capacitor circuit generally comprising a current limit resistor 3 connected in series to a power source 1, a transistor 4, a capacitor 2, and a wire electrode 5. As the wire electrode 5 approaches the workpiece, the capacitor starts to discharge, and to produce an electric discharge between wire electrode 5 and workpiece 6 to perform a cutting process. Because of the limitation of charging and discharging time of the capacitor and the problem of energy control during the discharging of the capacitor, the wire cut EDM cannot achieve a high processing speed.